Method of alloying magnesium with manganese



Patented Nov. 4, 1941 ma'rnon OF ALLOYING MAGNESIUM WITH MA NE E Charles E. Nelson and George F. Gunn, Midland,

Mich assignors to The Dow Chemical Company, Midland, Mich, a corporation of Michisan N0 Drawing. Application April 25, 1941,

'Serial No. 390,365

10 Claims.

The present invention relates to a method of alloying or otherwise treating magnesium or magnesium base alloys with manganese, in the presence of an inorganic flux, in such a manner that the flux has substantially the same fluxing characteristics after the alloying operation as before, and, hence, to this extent, equilibrium fiuxing conditions are maintained. The invention relates especially, but not exclusively, to a method as aforesaid where the amount of flux employed is of the order of 15 per cent or less of the Weight of the metal, and where the flux is materially and disadvantageously altered by the addition of manganese compounds alone.

It is standard practice to handle molten magnesium and molten magnesium base alloys in the presence of a flux consisting of a fused mixture of inorganic compounds, to prevent burning. The flux may be lighter than the alloy and form a crust over the surface of the molten metal, or it may be of such density that a part only of the flux remains over the metal as a film, the main body of the flux being beneath the metal. In some instances the flux is chosen for its ability to form a thin-skin over a part of the metal, leaving a portion of the surface uncovered.

It is also well known practice to alloy magnesium with manganese 'by introducing an an? hydrous reducible manganese compound into the molten magnesium. The commonest reducible manganese compound employed for this purpose is manganous chloride. When manganous chloride is added to molten magnesium, or magnesium base alloy, there is an almost instantaneous reduction to metallic manganese, accompanied by the formation of magnesium chloride in amount equivalent to the chlorine introduced in the manganese chloride. The magnesium chloride so formed becomes part of the inorganic fluxsystem, thereby changing the composition of the said system. The flux cannot, therefore, be re-used indefinitely in the same type of operation because of its changed composition, and, even in the same melt, it no longer serves its original function to, the desired extent. The care exercised in selecting the original flux has thus been defeated. It becomes apparent, therefore, that means should be provided whereby the flux composition after an alloying operation may be of substantially the same fluxing characteristics as that present before the addition of the reducible manganese compound.

It is, accordingly, an object of the invention to provide a method whereby magnesium or magnesium base alloys may be alloyed with manganese by interaction with a reducible manganese compound, in, the presence of an inorganic flux, such that the flux composition, after the introduction of the said reducible manganese compound, has substantially the same fluxing characteristics as had that originally present before the introduction of. the manganese compound. Another object is to provide compositions of matter containing reducible manganese compounds, for addition to molten magnesium or its alloys, such that, after reaction has occurred between the magnesium and the reducible manganese compound, the flux composition is'substantially identical as to analysis and/or fluxing properties as that previously present. A further object is to provide a method and composition as afore said whereby equilibrium fluxing conditions'may be maintained to the extent indicatednamely, that the flux present after reduction of the manganese compound and that present before its in troduction are of substantially the same c'ompo sition. A particular object is to provide a method and composition as set forth in the preceding objects, wherein the reducible manganese compound is substantially anhydrous (ST -per cent or better) manganous chloride. 'Other objects and advantages of the invention will become apparent from the following description.

It has 'now been found that the foregoing and related objects may be attained and the advantages accruing thereto may be secured, by melting magnesium or ja magnesium base alloy in the presence of a flux of inorganic compounds and adding to the fmolten mixture a reducible manganese compound at least in quantity sufficient to form the desired alloy, together with supplemental flux ingredients, the supplemental flux mixture, including the reducible manganese compound, being in such proportion that on reaction between molten magnesium and the'rnan ganese compound there is formed a "final flux mixture of the same fiuxing characteristics as the original flux.

na ef ed emb diment e i ntion prises the steps of melting magnesium, or magbase alloys, in the presence of a flux of inorganic compounds including the magnesium analog of the reducible manganese compound to be employed, and adding to the molten mixture 2. reducible manganese compound at least in quantity sufficient to form the desired alloy, to-

gether with supplemental flux ingredients free f o he ma e m an o f e red cib e manga e e c mpound em loye h in edient of the supplemental flux, including the reducible manganese compound, being in such proportion that on reaction between molten magnesium and the manganese compound there is formed a sufficient additional amount of the magnesium compound originally present to give the final flux mixture substantially the same fiuxing characteristics as the original flux. In a specific embodiment, the supplemental flux ingredients are in a proportion such that the reduction of the manganese compound forms enough of its magnesium analog to give the final flux substantially the same analysis as the original flux.

The term original flux herein employed refers to the mixture of inorganic compounds in contact with which the original magnesium or magnesium base alloy was molten prior to addition of the manganese compound. The term final flux refers to the inorganic compound mixture present as flux after reaction with the manganese compound. Supplemental flux or balance flux are terms employed to indicate the mixture of inorganic compounds, including a reducible manganese compound, added to the original melt to supply the manganese needed for alloying with the magnesium and/or for settling iron and similar impurities therefrom. The term magnesium analog of the manganese compounds employed can best be defined by means of example: Thus, magnesium oxide is deemed to be the analog of manganous oxide, magnesium fluoride to be the analog of manganous fluoride, and magnesium chloride to be the analog of manganous chloride. In the following description and claims, the term magnesium will be understood to include not only magnesium itself but also those alloys in which it predominates, generally referred to as magnesium base alloys. The expression substantially the same fluxing characteristics as those of the original-flux is .employed in connection with the final flux to indicate the condition thereof. as compared with that of the original flux, and this condition is recognized by a skilled operator by a visual inspection of the molten mass and an observation of the film-forming, crust-forming, or flow characteristics of the flux.

According to the invention, the supplemental flux, which in the commonest and preferred embodiment of the invention containsno magnesium analog of the reducible manganese compound present, usually contains all of the other ingreclients of the original flux, although one or more of these compounds may be omitted or their proportions altered if the final flux will have the same fiuxing characteristics as the original flux, without supplementing the amount of these particular compounds, as will be shown more fully hereinafter.

The following examples illustrate the practice of the invention but are not to be construed as limiting:

Example 1 Magnesium is melted in the presence of a flux consisting of Per cent Potassium chloride 55 Calcium fluoride 2 Barium chloride 9 Magnesium chloride 34 quired amount of manganese to form the desired Mg-Mn alloy, a supplemental flux mixture consisting of Per cent Manganous chloride 38 Potassium chloride 48 Calcium fluoride 5 Barium chloride 9 The supplemental flux is stirred into the original melt and the manganous chloride reacts at once. The final flux has substantially identical fiuxing properties with those of the original flux. The proportion of calcium fluoride is higher in the balance flux than in the original flux, but this is of value in maintaining the film properties of the flux over the metal surface.

Example 2 To a batch of molten magnesium in the presence of the same original flux as was employed in the preceding example is added a supplemental flux having the following analysis Per cent Manganous chloride 72 Potassium chloride 23 Calcium fluoride 2.5 Barium chloride 2.5

After the supplemental flux is stirred into the mixture, the final flux has the same fusion characteristics and general fluxing properties as has the original flux.

Example 3 It is desired to treat a magnesium base alloy with about 2 per cent of its weight of manganese. 900 pounds of a predominantly magnesium metal is melted in the presence of an original flux consisting of 44 per cent of sodium chloride and 56 per cent of magnesium chloride. To the batch is added '78 pounds of a mixture consisting of 66 per cent manganous chloride and 34 per cent sodium chloride. The supplemental flux is stirred in the, usual manner with the molten magnesium, with which it reacts rapidly. The final fiux has the same chemical analysis and hence the same fluxing characteristics as the original flux.

The same original flux and the same supplemental flux may be employed to produce magnesium-manganese alloys of varied manganese content by employing for each 1000 pounds of molten magnesium the following amounts of supplemental flux of the above-stated analysis to provide the indicated amount of manganes for alloying with, or treating the magnesium. The quantities in the table are based on 80 per cent alloying efilciency for the manganese chloride. In each instance the flnal flux is of substantially the same analysis as the original flux.

Desired Pounds supplepercent mental flux per manganese 1000 pounds in alloy magnesium 0. l 4. 5 0.2 9. 0 0. 3 l3. 5 1. 0 46. 5 l. 3 60.0 1. 5 68.0 2. 0 93.0

Example :4

It is desired to treat a magnesium base alloy containing aluminum and zinc with about 1 per cent of manganese. 1000 pounds of the alloy s melted in a suitable crucible with about 20 pounds of a flux consisting of Per cent Potassium chloride 20 Calcium fluoride 17.5 Magnesium chloride 45 Magnesium oxide 17.5

This flux forms a crust over the top of the alloy as contrasted with the usual fluid film provided by the fluxes described in the preceding examples. To the melt is now added about 15 pounds of a supplemental flux consisting of Per cent Manganous chloride '70 Calcium fluoride 15 Magnesium oxide 15 This supplemental flux contains a large amount of manganese chloride and no potassium chloride, yet the final flux has substantially identical fluxing characteristics with those of the original flux. Had the supplemental flux in this case contained potassium chloride, experience has shown that the large amount of magnesium chloride formed during the alloying operation co-operates with the potassium chloride present to provide a greater fluidity in the final flux than that exhibited by the original flux.

Example 5 To provide an alloy of magnesium with 1.5 per cent of manganese, 800 pounds of magnesium is melted in the presence of an original flux consisting of Per cent Magnesium chloride 66 Barium chloride 5 Potassium chloride 29 To the molten mixture is added 47.5 pounds of a supplemental flux composition consisting of Per cent Manganous chloride 72 Barium chloride 4.1 Potassium chloride 23.9

The supplemental flux is stirred with the magnesium at a temperature of about 1325 F. The

manganous chloride is rapidly reduced to man- The following additional examples illustrate the use of supplemental fluxes containing reducible manganese compounds other than the chloride, or they illustrate original fluxes free from the magnesium analog of the manganese compound employed, or both.

Example '6 500 parts by weight of magnesium is molten in the presence of 50 parts by weight of an original flux consisting of Per cent Potassium chloride 20 Calcium fluoride 17.5 Magnesium chloride Magnesium oxide 17.5

To the melt is added 132 parts by weight of a supplemental flux, containing enough manganese compound to provide 1 per cent of manganese in the resulting alloy, and consisting of Per cent Potassium chloride 40 Calcium fluoride 10 Manganous oxide The flux-ing characteristics of the final flux are substantially the same as those of the original flux. When, however, larger amounts of the supplemental flux are added, the final flux begins to thicken appreciably, but addition of small amounts of original flux mixture again gives the same fluxing characteristics as those originally observed.

Example 7 500 parts of magnesium is molten with 50 parts by weight of an original flux consisting of Per cent Potassium chloride 51 Lithium chloride 44 Potassium fluoride 5 There is added 38.3 parts of a supplemental flux consisting of Per cent Potassium chloride 35 Lithium chloride 30 Potassium fluoride 5 Manganous chloride 30 to provide about 1 per cent of manganese in the resulting alloy. Th final flux coalesces and protects the metal and has the same fluxing characteristics as does the original flux.

Example 8 500 grams of an alloy consisting of about 91 per cent magnesium, about 6 per cent aluminum and about 3 per cent zinc, is melted with 50 parts of the same original flux employed in Example 7. A quantity (5.4 parts) of supplemental flux, sufficient to introduce about 0.5 per cent of manganese, is added, consisting of Per cent Potassium chloride 15 Lithium chloride 15 Potassium fluoride 10 Manganous oxide In the relative proportions recited, the mixture gives a final flux with the same characteristics as the original, but when the supplemental flux is added in larger amounts, to provide the equivalent of from 1 to 2 per cent of manganese, the flux, while still giving good protection andvhav ing good coalescence properties, begins to thicken considerable. For making one of the common commercial alloys of Mg6Al-0.2-0.5Mn3Zn, the fluxes here reported are entirely satisfactory and their use is contemplated within the terms of the appended claims.

Example 9 To 500 parts by weight of the same alloy as was employed in Example 8, is added 50 parts of an original flux composition consisting of Per cent Calcium chloride 60 Calcium fluoride 15 Barium fluoride 25 The mixture is melted and held at about 700- 750 C. There is added 42.4 parts by weight of a supplemental flux consisting of Per cent Calcium chloride 50 Calcium fluoride 10 Barium fluoride 20 Manganous fluoride 20 Up to the stated amount of supplemental flux, the final flux has the same characteristics as the original flux, and the molten metal has an especially bright appearance. Continued addition of supplemental flux beyond the amount stated, which yields 1 per cent of manganese for alloying or settling purposes, still gives a fluid protective coating which, however, tends to open up over the melt. This change does not occur, however, when introducing the customary 0.2 to 0.5 per cent of manganese into the stated alloy.

The foregoing Examples 6-9, inclusive, have illustrated the use of manganese oxide and fluoride as reducible manganese compounds, in addition to the chloride previously illustrated and commonly employed. It is to be understood that other reducible manganese compounds may be employed in like manner, and that the compositions shown in the examples have been given purely by way of illustration. In none of Examples 69, inclusive, does the original flux contain the magnesium analog of the manganese compound employed in the supplemental flux, and in each case the supplemental flux is also free from the said magnesium analog.

It is observed that the present method offers several advantages over the heretofore employed methods, both as to the fluxing conditions and as to the method of alloying magnesium with other common alloying metals. For instance, it is now possible in a single heat to melt magnesium, add aluminum or a mixture of aluminum and zinc, stir the so-formed mixture to produce a magnesium-aluminum or magnesium-aluminum-zinc alloy, and, without disturbing the physical characteristics of the flux, to incorporate the desired amount of manganese into the alloys by means of the herein described supplemental flux composition. The final flux present, after the alloying operation is complete, as herein described, may be re-employed almost indefinitely in subsequent operations of like character, in view of the fact that it has the same fusion characteristics as hadthe original flux. According to past practice, when manganous chloride is added alone to a fluxed molten magnesium bath, the additional magnesium chloride produced upsets the equilibrium in the fluxing conditions and may alter either the density or the fusion characteristics of the inorganic flux mixture, thereby making further handling of the melt more difficult than has now been shown to be necessary.

The invention is of particular advantage where small total amounts of flux, e. g. per cent or less, are employed with large amounts of metal, as in such cases the reaction between the metal and the manganese compound alone introduces enough magnesium compound into the flux system to alter its composition and fusion characteristics materially. When, however, the manganese compound is added in a balance flux of the herein described type, the fluxing conditions are substantially undisturbed.

This application is a continuation-in-part of our co-pending application Serial No. 332,702, filed May 1, 1940.

Other modes of applying the principle of our invention may be employed instead of those explained, change being made as regards the method herein disclosed, provided the step or steps stated by any of the following claims or the equivalent of such stated step or steps be employed.

We therefore particularly point out and distinctly claim as our invention:

1. In a method of alloying magnesium with manganese by interaction with a reducible manganese compound, the steps which comprise melting magnesium in the presence of a protective flux, and adding to the molten mixture a supplemental flux containing a reducible manganese compound, in quantity at least sufficient to form the desired alloy, and. other flux ingredients, the said supplemental flux mixture being of such compositional proportion that, on reaction between the molten magnesium and the manganese compound, there is formed a final flux mixture of substantially the same fluxing characteristics as those of the original flux.

2. In a method of alloying magnesium with manganese by interaction with a reducible manganese compound, the steps which comprise melting magnesium in the presence of an amount of protective flux, such that upon addition of the required amount of reducible manganese compound alone there is formed enough of the magnesium analog of said manganese compound to alter materially the fluxing characteristics of the flux, and adding to the molten mixture of magnesium and original flux a supplemental flux containing a reducible manganese compound, in quantity at least suflicient to form the desired alloy, and other flux ingredients, the said supplemental flux mixture being of such compositional proportion that, on reaction between the molten magnesium and the manganese compound, there is formed a final flux mixture of substantially the same fluxing characteristics as those of the original flux.

3. In a method of alloying magnesium with manganese by interaction with a reducible manganense compound, the steps which comprise melting magnesium in the presence of less than 15 per cent of its weight of a protective flux and adding to the molten mixture a supplemental flux containing a reducible manganese compound, in quantity at least suflicient to form the desired alloy, and other flux ingredients, the said supplemental flux mixture being of such compositional proportion that, on reaction between the molten magnesium and the manganese compound, there is iormed a final flux mixture of substantially the same fluxing characteristics as those of the original flux.

4. In a method of alloying magnesium with manganese by interaction with a reducible manganese compound, the steps which consist in melting magnesium in the presence of a protective flux including th magnesium analog of the reducible manganese compound to be employed,

and adding to the molten mixture a reducible manganese compound, in quantity at least sufficient to form the desired alloy, and supplemental flux ingredients substantially free from the magnesium analog of the reducible manganese compound employed, the ingredients of the supplemental flux mixture being of such compositional proportion that, on reaction between th molten magnesium and the manganese compound, there is formed a suflicient additional amount of the magnesium analog of the manganese compound employed to give the final flux mixture substantially the same fluxing characteristics as those of the original flux.

5. In a method of alloying magnesium with manganese by interaction with a reducible manganese compound, the steps which consist in melting magnesium, in the presence of an amount of a protective flux, including the magnesium analog of the reducible manganese compound to be employed, such that upon addition of th required amount of reducible manganese compound alone there is formed enough of the magnesium analog of said manganese compound to alter materially the fluxing characteristics of the flux, and adding to the molten mixture of magnesium and original flux a supplemental fiux containing a reducible manganese compound, in quantity at least suflicient to form the desired alloy, and other flux ingredients, substantially free from the magnesium analog of the reducible manganese compound employed, the ingredients of the supplemental flux mixture being of such compositional proportion that, on reaction between the molten magnesium and the manganese compound, there 55 is formed a sufficient additional amount of the magnesium analog of th manganese compound employed to give the final flux mixture substantially the same fluxing characteristics as those of the original flux.

6. In a method of alloying magnesium with manganese by interaction with man anous chloride, the steps which consist in melting magnesium in the presence of an amount of a protective flux such that upon addition of the required amount of reducible manganous chloride alone there is formed enough magnesium chloride to alter materially the characteristics of the flux, and adding to the molten mixture of magnesium and original flux a supplemental flux containing manganous chloride, in quantity at least sufiicient to form the desired alloy, and other flux ingredients, the said supplemental fiux mixture being of such compositional proportion that, on reaction between molten magnesium and the manganous chloride, there is formed a final flux mixture of substantially the same fiuxing characteristics as those of the original flux.

'7. In a method of alloying magnesium with manganese by interaction with manganous chloride, the steps which consist in melting magnesium in the presence of a protective flux, including magnesium chloride, and adding to the molten mixture a supplemental flux containing manganous chloride, in quantity at least sufiicient to form the desired alloy, and other flux ingredients, substantially free from magnesium chloride, the ingredients of the supplemental flux mixture being of such compositional proportion that, on reaction between molten magnesium and manganous chloride, there is formed sufiicient additional amount of the magnesium chloride to give the final flux mixture substantially the same fluxing characteristics as those of the original flux.

8. In a method of alloying magnesium with manganese by interaction with manganous chloride, the steps which consist in melting magnesium in the presence of a flux consisting of Percent Potassium chloride about 55 Calcium fluoride about2 Barium chloride about9 Magnesium chloride about 34 adding to the molten mixture a supplemental flux consisting of Percent Manganous chloride about 38 Potassium chloride about 48 Calcium fluoride about 5 Barium chloride about9 and stirring the said supplemental flux into the molten mixture, thereby to reduce the manganous chloride and to produce a final flux mixture of substantially th same fiuxing characteristics as those of the original flux.

' 9. In a method of alloying magnesium with manganese by interaction with manganous chloride, the steps which consist in melting magnesium in the present of a flux consisting of Percent Potassium chloride about 20 Calcium fluoride about 17.5 Magnesium chloride about 45 Magnesium oxide about 17.5

adding to the molten mixture a supplemental flux consisting of 1 Percent Manganous chloride about 70 Calcium fluoride about 15 Magnesium oxide about 15 and stirring the said supplemental fiux into the molten mixture, thereby to reduce the manganous chloride and to produce a final flux mixture of substantially th same fluxing characteristics as Percent Magnesium chloride about 66 Barium chloride about5 Potassium chloride about 29 adding to the molten mixture a supplemental flux consisting of Percent Manganous chloride about 72 Barium chloride about 4.1 Potassium chloride about 23.9

and stirring the said supplemental flux into the molten mixture, thereby to reduce the manganous chloride and to produce a final flux mixture of substantially the same fiuxing characteristics as those of th original flux.

CHARLES E. NELSON. GEORGE F. GUN'N. 

